Dispersant additives containing phosphorus,sulfur and nitrogen

ABSTRACT

TO PREPARE ADDITIVES FOR FUEL AND LUBRICANT COMPOSITIONS, PHOSPHOSULFURIZED HYDROCARBONS ARE REACTED WITH AZIRIDINE COMPOUNDS. THE REACTION PRODUCTS ARE PARTICULARLY USEFUL FOR IMPARTING DISPERSANCY TO LUBRICANT COMPOSITIONS. A REPRESENTATIVE DISPERSANT IS PREPARED BY REACTING POLYISOBUTYLENE WITH PHOSPHORUS PENTASULFIDE AND THEN REACTING THE RESULTING PHOSPHOSULFURIZED POLYISOBUTYLENE WITH ETHYLENIMINE. THE PRODUCTS CAM BE MODIFIED BY FURTHER REACTION WITH METAL ALCOHOLATES OR METAL SALTS OF FATTY ACIDS SUCH AS ZINC ACETATE.

United States Patent Office 3,826,797 Patented July 30, 1974 3,826,797 DISPERSANT ADDITIVES CONTAINING PHOS- PHORUS, SULFUR AND NITROGEN Stanley J. Brois, Englishtown, N.J., assignor to Esso Research and Engineering Company No Drawing. Filed Mar. 24, 1972, Ser. No. 237,985 Int. Cl. C07g 17/00; C10m 1/48 US. Cl. 260-425 13 Claims ABSTRACT OF THE DISCLOSURE To prepare additives for fuel and lubricant compositions, phosphosulfurized hydrocarbons are reacted with aziridine compounds. The reaction products are particularly useful for imparting dispersancy to lubricant compositions. A representative dispersant is prepared by reacting polyisobutylene with phosphorus pentasulfide and then reacting the resulting phosphosulfurized polyisobutylene with ethylenimine. The products can be modified by further reaction with metal alcoholates or metal salts of fatty acids such as zinc acetate.

FIELD OF THE INVENTION The present invention concerns multifunctional dispersant additives for oil compositions including gasoline, fuel oil, heating oil and lubricating oil. It also concerns the preparation of such additives and oil compositions containing them. The additives are further characterized as oilsoluble reaction products of phosphosulfurized hydrocarbons with aziridines.

Numerous addition agents are known in the prior art for improving the desirable properties of fuel and lubricants, including resistance to deterioration and freedom from the formation of insoluble sludge or the ability to disperse any insoluble products that are formed during use. Additives that will impart good dispersancy to lubricants and fuels are particularly desirable. By dispersancy is meant primarily the prevention of the deposition of insoluble material from the composition. Emphasis in this field in recent years has been placed on development of metal-free additives that will not form an ash. While ashfree dispersants are of particular value in lubricant compositions, they are also used advantageously in diesel fuels, fuel oil compositions, and gasolines as well.

REFERENCES TO THE PRIOR ART It is known to prepare oil-soluble dispersant additives by treating hydrocarbons, particularly olefin polymers, with sulfides of phosphorus followed by reaction of the phosphosulfurized hydrocarbons with aliphatic amines or alkylene polyamines. Thus solvent-extracted lubricating oil stocks have been phosphosulfurized and then reacted with primary or secondary amines (U.S. Pat. 2,809,934); thiophosphonic acids derived by the hydrolysis of phosphosulfurized hydrocarbons have been reacted with aliphatic amines or alkylene polyamines (U.S. Pats. 3,143,506 and 3,185,728); and phosphosulfurized hydrocarbons have been reacted directly with amines or polyamines without hydrolyzing the phosphosulfurized hydrocarbons (U.S. Pats. 3,329,612 and 3,560,384 and British Pat. 970,880).

DESCRIPTION OF THE INVENTION It has now been found in accordance with the present invention that a highly effective dispersant for a lubricating oil or fuel composition can be prepared by the interaction of a phosphosulfurized hydrocarbon with an aziridine compound. Aziridine itself is also known as ethylenimine. These dispersants differ chemically from those obtained by reaction of aliphatic amines or polyamines with phosphosulfurized hydrocarbons and also exhibit more effective dispersancy action than those of the latter type.

The aziridines that are suitable for use in this invention can be characterized by the formula:

C H RIII wherein each of R, R, R" and R" represents hydrogen, or an alkyl or aryl group. The alkyl group will have from 1 to 18 carbon atoms, most usually about 1 to 12 carbon atoms. The aryl groups will have from about 6 to 12 carbon atoms. Preferably R, R, R" and R'" are either hydrogen or alkyl. A particularly suitable aziridine is ethyleneimine wherein each of R, R, etc. in the above formula is hydrogen. Other representative aziridines include the l-alkyl derivatives or l-aralkyl derivatives, i.e., where R is alkyl or aralkyl and each of the R, R" and R'" is hydrogen, e.g., l-methyl, l-ethyl, l-butyl, l-cyclohexyl, l-benzyl, l-octadecyl, or l-phenethyl; l-substituted alkyl groups having additional functional groups on the alkyl chain such as l-(carboalkoxyalkyl), '1-(2-hydroxyethyl), l-cyanoethyl, l-(omega-aminoalkyl), etc.; 2-alkylaziridines, i.e., where R is alkyl and R, R and R' are hydrogen, e.g., 2-methyl-, 2-etl1yl-, 2-butyl-, 2-octadecyl-, or 2-benzylazin'dine; and aziridines having two or more substituents, such as 1,2-dimethyl-, 2,2-dimethyl-, l-methylphenyl-, 1 tertbutyl 2 phenyl-, 2,3-dimethyl-, 1,2,2-trimethyl-, and 2,2,3-trimethylaziridine.

The preparation of phosphosulfurized hydrocarbons is well known in the art and simply involves reaction of a sulfide of phosphorus such as P S P S and so forth with a suitable hydrocarbon material such as a heavy petroleum fraction, an olefin, an olefin polymer or copolymer, or a terpene. The actual structure of phosphorus pentasulfide is considered to be P 5 although P S is used as the designation in the specification in keeping with common practice. The reaction between the hydrocarbon and the sulfide of phosphorus is normally conducted under anhydrous conditions, preferably in a nonoxidizing atmosphere, e.g., nitrogen, at temperatures of from about 70 to about 300 C., or more usually about to 250 C., for from about 1 to 50 hours, more usually about 1 to 15 hours, using about 5 to about 40 parts by weight of the sulfide of phosphorus per 100 parts of the hydrocarbon. A convenient procedure for assessing completion of the reaction is to use what is known as the white spirit test, which involves mixing one volume of the reaction mixture with 3 to 6 volumes of hexane. If a clear solution results, with no detectable turbidity, after about 15 minutes, the reaction is virtually complete. It is ordinarily preferred to employ a proportion of phosphorus sulfide that will react completely with the hydrocarbon so that no purification of the phosphosulfurized hydrocarbon will be required before proceeding with reaction with the aziridine.

Particularly useful hydrocarbons for the phosphosulfurization reaction include the polymers of C to C monoolefins, e.g., ethylene, propylene, butylene, isobutylene and pentene. The polymers can be homopolymers such as polyisobutylene as well as copolymers or two or more of such olefins such as a copolymer of butylene and isobutylene or of propylene and isobutylene. Still other co polymers that can be used include those in which one of the monomers is a diolefin, e.g., a copolymer of isobutylene and butadiene or a copolymer of ethylene, propylene and 1,4-hexadiene.

The polymers will have average molecular weights within the range of about 500 and about 100,000, or more usually between about 800 and about 20,000. Particularly useful olefin polymers have average molecular weights within the range of about 900 and about 3000 with approximately one double bond per polymer chain. An espe-,,

cially valuable starting material for a highly potent dispersant additive made in accordance with this invention is polyisobutylene having an average molecular weight in the range of about 1900 to about 2300. Molecular weights are conveniently determined by osmometry.

Especially useful when it is desired it is desired that the dispersant additives also possess viscosity index improving properties are 25,000 to 100,000 average molecular weight terpolymers of ethylene-propylene and a diene, e.g., a terpolymer of 25 to 75 weight percent propylene, 2 to 9 weight percent of a diene such as 1,4-hexadiene, ethylidene norbornene, methylene norbornene, dicyclopentadiene, etc.

For olefin polymers with about one double bond per chain, as for example in polyisobutylene, the amount of P 8 used will usually be between about 0.2 and 2 moles per mole of olefin polymer. In the case of 1900 to 2300 molecular weight polyisobutylene it is advantageous to use from about 0.4 to 2 mole of P 8 per mole of polyolefin.

In the case of high molecular weight terpolymers such as those of ethylene, propylene and a diene it is preferred to use about 1 to 2 moles of P 8 per mole of diene monomer component (e.g. ethylidene norbornene or 1,4-hexadiene) although as little as 0.2 mole and as much as 2 moles of P 8 can be used per mole of diene component.

Although it is not usually necessary, it is sometimes convenient to employ an inert solvent or diluent in the phosphosulfurizing reaction, particularly where the polymeric material is highly viscous or solid.

In the reaction of the phosphosulfurized hydrocarbon with an aziridine, the aziridine can be added to the phosphosulfurized hydrocarbon as such or diluted in a suitable solvent such as pentane, hexane, tetrahydrofuran, diethyl ether and so forth. The use of a solvent helps to moderate large scale reactions and also aids in mixing. A convenient solvent is a lubricating oil fraction which has the advantage of thereby forming an additive concentrate which can easily be blended into a finished lubricating oil composition. Typically an equal volume of solvent and phosphosulfurized hydrocarbon will be used. Generally the reaction temperature will be ambient temperature although temperatures between about C. and about 100 C. can be used. Usually the reaction is exothermic so that external cooling will be applied to maintain a desired reaction temperature. The reaction of the aziridine with the phosphosulfurized hydrocarbon will normally be conducted under atmospheric pressure although pressures higher than atmospheric can be employed. The reaction will normally take about one to 2 hours although in some instances as many as 2 to 30 hours may be required to ensure that all of the aziridine has been incorporated into the product. In the case of exothermic reactions, the reaction can be monitored by determining when no more heat is evolved in the reaction. Gas chromatographic analysis can also be used to monitor the reaction.

The amount of aziridine used in the reaction can range between about one and about 6 moles per atom of phosphotos in the phosphosulfurized hydrocarbon. Preferably between about one and about 4 mole equivalents of aziridine will be used per atom of phosphorus.

At the end of the reaction the product can be freed of any unreacted aziridine, if any is present, by heating the product under vacuum. This will also serve to remove the more volatile solvents if such are used as well as any other volatile components that need to be removed from the product.

While it is not intended that this invention be limited by any theory, and although the stoichiometry of the reactions involved in this process is not precisely known, it is believed that the reaction of an olefin polymer with P 8 under suitable conditions engenders, inter alia, perthiophosphonic acid anhydrides, which may be represented by such heteroadamantane structure as:

wherein either R or R is the residue of the olefin polymer chain, and the remaining ones of R and R are hydrogen or alkyl.

It is believed that the perthiophosphonic acid anhydrides undergo reaction with aziridine molecules to give products that contain Z-thiono-1,3,2-thiazaphospholane rings, e.g. a structure of the following type:

It is envisaged that compound B, and related structures will react further with excess aziridine, reaching a limit of about 2 to 3 moles of the aziridine per atom of phosphorus.

In one embodiment of this invention, the phosphosulfurized hydrocarbon can be treated for from 1 to 48 hours at ambient temperature or at a temperature as high as reflux temperature with methanol or with a mixture of methanol and water containing less than 50% water, eg a mixture of 4 volumes of methanol and one of water, prior to the reaction with an aziridine. Preferably the methanol is used in stoichiometric excess with respect to the phosphosulfurized hydrocarbon, most preferably at least 3 molar equivalents of methanol 'per molar equivalent of the phosphosulfurized hydrocarbon. Other lower alcohols of up to 3 carbon atoms such as ethyl alcohol or isopropyl alcohol can be used instead of or in conjunction with methanol. The products obtained by the alcohol treatment are believed to be thiophosphonic acid derivatives, which may be represented as follows:

R 5 SH (Emi io w wherein R and R are as in Formula A, R is hydrogen, methyl, ethyl, propyl, or isopropyl, and T is hydrogen or s l sH Upon reaction of the alcohol-treated material with aziridine, it is believed that products having the following formula are produced.

wherein R, R and R are as in Formula C, and Y is As an alternative to the treatment with a lower alcohol, the phosphosulfurized hydrocarbon can be subjected to a hydrolysis step as, for example, by treatment with steam at 100 to 250 C. for 1 to 6 hours using a nonoxidizing protective atmosphere as, for example, a blanket of nitrogen. This treatment converts the phosphosulfurized hydrocarbon to a hydrocarbyl thiophosphonic acid.

In another embodiment of the invention, the reaction product of an aziridine and a phosposulfurized hydrocarbon in the form of its solution in a suitable solvent such as hexane, or cyclohexane, or a solvent neutral lubricating oil can be subjected to a solvent wash with an alcohol such as methanol or ethanol or a water-methanol mixture to improve the efiicacy of the resulting dispersant. This alcohol wash removes sediment-forming components or sludge-forming components as well as less effective fractions of the dispersant additive.

A particular embodiment of the invention involves the further reaction of the product of the aziridine reaction with a metal salt of a C to C fatty acid or a metal alcoholate of a C to C monohydric alcohol. The salts or alcoholates may be of such metals as zinc, cadmium or lead. Preferably the metal salt or metal alcoholate is of a lower fatty acid of from 1 to 4 carbon atoms or of a lower alcohol of from 1 to 4 carbon atoms to facilitate the removal of the fatty acid or alcohol generated in this reaction. Zinc salts or zinc alcoholates are preferred; these include zinc acetate, zinc formate, zinc ethoxide, zinc isopropoxide, and so forth. The reaction can be conducted at ambient temperatures or at slightly elevated temperatures, e.g., 30 to 40 C. and can be conducted simply by adding the metal salt or metal alcoholate to the neat product or to the product dissolved in a suitable solvent such as tetrahydrofuran. The amount of metal alcoholate or carboxylate used can range from about 0.01 to about 1 mole equivalent of metal per atom of phosphorus in the aziridine-treated phosphosulfurized hydrocarbons. Preferably between about 0.05 to 0.5 mole equivalent of metal salt is used per atom of phosphorus.

The additives of this invention will be employed in concentrations ranging from about 0.001 to about 10 weight percent in oil compositions ranging from gasoline fractions through middle distillate fuels and lubricating oils.

For use as lubricating oil additives the reaction prodnets of this invention can be incorporated in lubricating oil compositions in concentrations within the range of from about 0.1 to about 10 Weight percent and will ordi narily be used in concentrations of from about 0.1 to about 5 weight percent. The lubricating oils to which the additives of the invention can be added include not only mineral lubricating oils, but synthetic oils also. The mineral lubricating oils may be of any preferred types, including those derived from the ordinary parafiinic, naphthenic, asphaltic, or mixed base mineral crude oils by suitable refining methods. Synthetic hydrocarbon lubricating oils may also be employed, as well as nonhydrocarbon synthetic oils, including dibasic acid esters such as di-2-ethyl hexyl sebacate, carbonate esters, phosphate esters, halogenated hydrocarbons, polysilicones, polyglycols, glycol esters such as C oxo acid diesters of tetraethylene glycol, and complex esters, as for example the complex ester formed by the reaction of 1 mole of sebacic acid with 2 moles of tetraethylene glycol and 2 moles of 2-ethyl hexanoic acid.

The additives of this invention can also be employed in middle distillate fuels for inhibiting corrosion and the formation of sludge and sediment in such fuels. Concentration ranges of from about 0.002 to about 2 weight percent, or more generally from about 0.005 to about 0.2 weight percent are employed. Petroleum distillate fuels boiling in the range of from about 300 to about 900 F. are contemplated. Typical of such fuels are No. 1 and No. 2 fuel oils that meet ASTM Specification D-396-48T, diesel fuels qualifying as Grades 1D, 2D and 4D of ASTM Specification D-97551T, and various jet engine fuels. Because they are ashless, these additives are particularly desirable for such fuels in that they do not give rise to glowing ashes nor deter from the burning qualities of the distillates. These additives can also be used in conjunction with other prior art ashless additives for fuels, such as polymers of acrylic or methacrylic acid esters, high molecular weight aliphatic amines, etc.

The additives of this invention can also beemployed either alone or in combination with other hydrocarbonsoluble additives, in jet fuels and gasolines in concentrations ranging from about 0.001 to 1.0 weight percent as detergent and/ or rust preventive additives.

In either the fuel or lubricant compositions, other conventional additives may also be present, including dyes, pour point depressants, antiwear agents, e.g. tricresyl phosphate, zinc dialkyl dithiophosphates of 3 to 8 carbon atoms, antioxidants such as phenyl-alpha-naphthylamine, tert. octylphenol sulfide bis-phenols such as 4,4-methy1ene bis(2,6-di tert. butylphenol), viscosity index improvers such as polymethacrylates, polyisobutylene, alkyl fumarate-vinyl acetate copolymers, and the like as well as other ashless dispersants or detergents.

The dispersant additives of the invention can also be used to enhance the dispersancy-detergency of lubricants containing conventional metal-containing detergents, pro vided no problem of incompatability arises, and thereby obtain added dispersancy or detergency without materially increasing the total ash-forming properties of the composition.

The nature of this invention will be further understood when reference is made to the following examples, which include preferred embodiments.

EXAMPLE 1 Phosphosulfurization of Polyisobutylene An 850 gram portion of polyisobutylene of 920 average molecular weight was placed in a reactor and heated to C. with stirring and nitrogen blowing. Then over a period of 30 minutes grams of P 8 was added, after which the temperature was increased to 235 C. At about 180 C. a vigorous reaction began, and care was necessary to prevent excessive foaming, which could be abated by careful control of the temperature. Reaction was completed in about 4 hours as determined by the white spirit test, earlier described. Analysis of the product showed a phosphorus content of 4.19 weight percent and a sulfur content of 7.5 weight percent.

EXAMPLE 2 Phosphosulfurization of Polyisobutylene A 200 gram portion of 2300 average molecular weight polyisobutylene was heated in a reactor to 180 C. with nitrogen blowing. Then over a period of 15 minutes 15 grams of P 8 was added at ISO- C., using rapid stirring and virogous purging with nitrogen to control foaming. Upon completion of P 8 addition the temperature was raised to 235 C. and reaction was continued at that temperature for about 4 hours, at which time a positive white spirit test showed that reaction was complete. The product was a clear ruby-colored liquid. Analysis showed a content of 2.20 weight percent phosphorous. A second batch prepared in the same manner analyzed 1.98 weight percent phosphorus.

EXAMPLE 3 Reaction with Ethylenimine A 1200 gram quantity of phosphosulfurized polyisobutylene prepared as described in Example 1 was diluted with 2 volumes of pentane and placed in a 5-liter fournecked flask fitted with stirrer, condenser, addition funnel and thermometer. Ethylenimine (450 ml.) was added slowly to the pentane solution which was kept below 32 C. using external cooling. The mixture was stirred overnight at room temperature and then concentrated to constant weight by removing pentane and unreacted aziridine under vacuum at 60-90 C. Elemental analysis showed that the nitrogen content of the clear, viscous liquid was 3.72%. The neat product was diluted with an equal weight of a refined lubricating oil known as Solvent 150N for subsequent bench tests and engine testing.

EXAMPLE 4 Reaction Variables The effects of type of solvent and varying stoichiometry in the reaction of ethylenimine with phosphosulfurized polyisobutylene were determined by a number of separate reactions, using as the phosphosulfurized hydrocarbon the product obtained by reaction of 150 parts of P 8 with 850 parts of a polyisobutylene having a molecular weight of about 920 as described in Example 1. Sulficient solvent was used to give about a 50 weight percent solution of reacting mixture. In some cases the procedure was modified by treating the phosphosulfurized hydrocarbon with methanol or a methanol-water mixture prior to reaction with ethylenirnine and in other cases similar treatment was applied to the reaction product. Each reaction was run at about 25 C. for about 8 to 10 hours, using external cooling to maintain the temperature.

In each instance, after the reaction had been completed the reaction product was heated in vacuo at about 1 to 10 millimeters mercury pressure at 60-90 C. for several hours to remove solvent, unreacted ethylenimine, and other volatile components such as water and alcohol from the additive product.

In those cases where 21 methanol wash or a methanolwater wash was used the procedure was as follows. First, 100 grams of the reactant or product to be washed was diluted to one liter of solution by adding pentane, and the pentane solution was washed 4 successive times with 250 milliliter aliquots of alcohol solvent (methanol or a mixture of 4 volumes of methanol and one volume of water), the alcohol layer being separated from the pentaue layer after each successive wash. The pentane solution after the final wash was freed of pentane by heating at 60- 90 C. under vacuum (10 mm. Hg pressure) for several hours until constant weight was obtained.

In Table I are given the reactant proportions, the solvents used, and the nitrogen contents of the final products. A ratio of 3 grams of ethylenimine to 50 grams of the particular phosphosulfurized polyisobutylene that was used is equal to about one equivalent of the aziridine per equivalent of phosphorous. In each case the nitrogen content is for the product without solvent; thus in those cases where the solvent was solvent 150 neutral lubricating oil, the found values have been doubled to allow for the fact that the products were obtained as 50 weight percent concentrates in oil.

TABLE I.REAC'IION WITH ETIIYLENIMINE (EI) Grams phosphosult'urized Wt. percent polyisobutyl- Grams nitrogen Solvent used one E1 in product I Values in all cases are for product ex solvent.

b Solvent 150 neutral refined lubricating oil.

0 Reactant methanol-washed before reaction with El.

d THE is tetrahydrofuran.

@ Reactant refluxed with methanol prior to reaction with E1. I Reaction product washed with methanol-water mixture.

8 EXAMPLE 5 Using the same general procedure as described in Example 4, separate portions of phosphosulfurized 920 molecular weight polyisobutylene, prepared as described in Example 1, were reacted with different N-substituted aziridines, namely N-(Z-aminoethyl) aziridine, N-(2- aminoethyl aminoethyl) aziridine, and N-(Z-aminoethyl aminoethyl aminoethyl) aziridine, which may be represented as:

HZC

where x is l, 2, or 3, respectively. Each aziridine was purified by fractional distillation prior to reaction, and was dissolved in about an equal volume of ethyl ether (Et O) or tetrahydrofuran (THF) prior to addition to the phosphosulfurize polyisobutylene.

The reactant proportions, the aziridine reactants and solvents used, and the nitrogen contents of the final products are shown in Table II.

TABLE II.REACTION WITH N-SUBSTlTUTED AZI RIDINES Grams Grams N- Wt. percent phosphosulturized substituted nitrogen polyisobutylene aziridine in product A-Using N-(2-aminoethyl) aziridine C-Using N-(Q-aminoethyl aminoethyl aminoethyl) aziridine Tetrahydrofuran used as solvent; unless thus indicated, the solvent was ethyl ether.

All products except this one were washed with methanol-water mixture as described in Example a fgieactant methanol-washed prior to reaction with the substituted EXAMPLE 6 Using the procedure described in Example 4, ethylenimine was reacted with separate phosphosulfurized polyisobutylenes prepared by treatment of 920 molecular weight polyisobutylene with 10, 18, and 22 weight percent P S respectively, and by treatment of 2300 molecular weight polyisobutylene with 7.5 and 11.1 weight percent P S respectively. The phosphosulfurized polyisobutylene can be conveniently designated by percent P S and molecular weight as IO-PSPIB-920, 18PSPIB920, 7.5PSPIB-2300, etc. Representative products, reactant proportions, and nitrogen analyses are given in Table III.

A zinc containing derivative of aZiridine-treated phosphosulfurized polybutene was prepared in the following manner.

A gram sample of phosphosulfurizcd 920 molecular weight polyisobutylene prepared as in Example 1 was first reacted with 12.9 grams of ethylenimine at room temperature. After stirring the reaction mixture at 25 C. for an hour, a slurry of 9.1 grams of zinc acetate in 100 ml. of tetrahydrofuran was gradually added over a 15 minute period. After continuous stirring at 25 C. for an hour, the reaction mixture became clear, indicating that all the zinc acetate had reacted. The homogeneous solution was freed of solvent and other volatile components by heating to constant weight at 6090 C. in vacuo (10 mm. Hg pressure). The nitrogen and zinc analyses for the product were found to be 1.58 and 2.44%, respectively.

EXAMPLE 8 The procedure of Example 7 was followed to prepare a zinc derivative that was derived from 2300 molecular weight polyisobutylene treated with 7.5 weight percent P 8 and which had then been reacted with ethylenimine. A 50 weight percent concentrate of the aziridine reaction product in 150 solvent neutral lubricating oil was used, 200 grams of the concentrate being added to 100 ml. of tetrahydrofuran. Then 3.1 grams of zinc acetate was added and the reaction mixture was heated under reflux for 8 hours. The product was filtered and then freed of solvent and other volatile components by heating to constant weight at 60-90" C. in vacuo. The nitrogen and zinc analyses for the product (50 weight percent concentrate in lubricating oil) were found to be 0.91 and 0.59%, respectively.

EXAMPLE 9 Sludge Dispersancy Tests A number of the additives of this invention were subjected to a sludge inhibition bench test which has been found, after a large number of evaluations, to be an excellent screening test for assessing the dispersing power of lubricating oil dispersant additives.

The medium chosen for the sludge inhibition bench test was a used crankcase oil having an original viscosity of about 325 SUS at 100 F. that had been used in a taxicab that was driven generally for short trips only, thereby causing a buildup of a high. concentration of sludge precursors. The oil that was used contained only a refined base oil, a viscosity index improver, a pour point depressant and zinc dialkyldithiophosphate antiwear additive. The oil contained no sludge dispersants. A quantity of such used oil was acquired by draining and refilling the taxicab crankcase at 1000-2000 mile intervals.

The sludge inhibition bench test is conducted in the following manner. The used crankcase oil, which is milky brown in color, is freed of sludge by centrifuging for 1 hour at 39,000 gs. The clear bright red supernatant oil is decanted from the insoluble sludge particles thereby separated out; however the supernatant oil still contains oil-soluble sludge precursors which on heating under the conditions employed by this test will tend to form additional oil-insoluble deposits of sludge. The sludge inhibiting properties of the additives being tested are determined by adding to portions of the supernatant used oil either 0.5, 1, or 2 weight percent, on an active ingredient basis, of the particular additive being tested. Comparison blends are also prepared using a standardized commercial dispersant. Ten grams of each blend being tested is placed in a stainless steel centrifuge tube and is heated at 280 F. for 16 hours in the presence of air. Following the heating, the tube containing the oil being tested is cooled and then centrifuged for 30 minutes at 39,000 gs. Any deposits of sludge that form in this step are separated from the oil by decanting the supernatant oil and then carefully washing the sludge deposits with 25 ml. of pentane to remove all remaining oil from the sludge. Then the weight of the solid sludge that has been formed in the test, in milligrams, is determined by drying the residue and weighing it. The results are reported as milligrams of sludge per grams of oil, thus measuring differences as small as 1 part per 10,000. The less sludge formed the more effective is the additive as a sludge dispersant.

Using the above-described test, the dispersant action of additives of the present invention was compared. with the dispersing power of a standardized commercial dispersant referred to as PIBSA/TEPA, with untreated phosphosulfurized polyisobutylene prepared as described in Example 1 and designated l5-PSPIB-920, and with reaction products of phosphosulfurized polyisobutylene and two different alkylene polyamines, namely ethylene diamine and tetraethylene pentamine. The latter two additives were prepared as described in British Pat. 970,880

and contained respectively 4.12% and 3.96% nitrogen on an active ingredient basis. The commercial dispersant designated PIBSA/TEPA was prepared by reaction of 1 mole of tetraethylene pentamine with 2.8 moles of polyisobutenyl succinic anhydride obtained from polyiso butylene of about 1000 number average molecular weight. This dispersant was obtained in the form of an additive concentrate containing about 50 weight percent of active ingredient in lubricating oil. The additive concentrate analyzed about 1.14% nitrogen, indicating that the active ingredient contained about 2.28% nitrogen. Suflicient quantities of the concentrate were used in making the test blends to furnish the required 0.5, l and 2 weight percent of actual additive. The test results are given in Table IV.

Wt. percent additive 2.0 1. 0 0. 5

PIBSA TEPA 2. 2 5. 2 7. 2

1 Refers to 5th product in Table I (4.00% N). 2 III-D, HI-E, III-F and III-G are designated products in Table III dispersant or the additives prepared in accordance with 1 British Pat. 970,880.

EXAMPLE 9 Engine Tests Fully formulated lubricating oil blends were prepared by blending 6.5 weight percent of ashless dispersant additive (50% a.i.), 6.9 weight percent of a viscosity index improver, 1.1% of a commercial zinc dialkyldithiophosphate antiwear additive (70% a.i.), 0.6 weight percent of sulfurized calcium nonyl phenate (50% a.i.) and 0.8 weight percent of the monolithium salt of dodecyl succinic anhydride (50% a.i.) into 84.1 weight percent of a refined lubricating oil base stock. The fully formulated lubricant had a viscosity in the SAE 10W30 range. In the above designations, 50% a.i. and 70% a.i. indicate that the additives thereby designated were used in the form of additive concentrates having the stated additive ingredient content. The weight percents stated for the formulations are of the concentrates used.

In one of the blends the dispersant was a product prepared in accordance with the present invention, identified as product F in Table III. In the other blend the dispersant additive was a product prepared by reaction of a technical mixture of alkylene polyamines predominating in tetraethylene pentamine and identified as Polyamine-H with the same phosphosulfurized polyisobutylene used in preparing the said additive F of Table III, i.e. 2300 molecular weight polyisobutylene reacted with 7.5% of P 3 The additive contained 2.84% nitrogen on a neat basis, i.e. without diluent. In both cases the dispersant additives were used in the form of 50% concentrates in lubricating oil.

Each of the blends prepared as described was subjected to MS Sequence V C Engine Test. This test was run in a Ford engine of 302 cubic inch displacement, following a procedure that is well known in the automotive industry. It is described in the publication entitled Multicylinder Test Sequences for Evaluating Automotive Engine Oils which is ASTM Special Publication 315-E. At the end of each test various parts of the engine are rated on a merit basis wherein 10 represents a perfectly clean part, and lesser numbers represent increasing degrees of depoist formation. The various ratings are then totaled and averaged on a basis of 10 as a perfect rating. The results obtained with the two blends described above are given in Table V.

TABLE V.-MS SEQUENCE V C TEST RESULTS [Merit ratings (basis 10)] It will be noted that the additive of the present invention was superior to the comparative product. The engine test results show that the additive of this invention is not only a good sludge dispersant but that it also possesses excellent oxidation control, as shown by the reduction in varnish deposits on the various engine parts, and particularly on the piston skirts. The favorable antioxidant properties of the dispersant additive of this invention will permit the formulation of a satisfactory crankcase lubricant without the need for additional conventional antioxidants.

The test data presented above clearly show that the dispersant powers of the additives of this invention are superior to those of the products of reacting phosphosulfurized hydrocarbons with polyamines, at comparable levels of heteroatom content, i.e. of phosphorus, sulfur and nitrogen. This difference in dispersing power could well be the result of differences in chemical structure. For example there is experimental evidence to indicate that the reaction with an aziridine gives rise to carbon-to sulfur bonds as a result of the well-known ring opening reaction of aziridines with sulfur compounds. Such a transformation is inherently not possible in the reaction of phosphosulfurized hydrocarbons with amines or polyamines.

As an added example of the preparation of a dispersant additive in accordance with this invention, a terpolymer of 62.5 weight percent ethylene, 34 weight percent propylene, and 3.5 weight percent 1,4-hexadiene, having an average molecular weight of about 24,000, is reacted with 18 percent of its weight of P 5 for 6 hours at 220 C. Then the phosphosulfurized terpolymer is treated with ethylenimine by the procedure shown in Example 3, using 3 equivalents of ethylenimine per equivalent of phosphorus in the phosphosulfurized terpolymer.

As disclosed supra, although the additives of this invention will be used in finished lubricant or fuel compositions in concentrations ranging from about 0.001 to about 10 percent by weight, it is also contemplated to use additive concentrates. Such concentrates can contain from about 10 to about 80 weight percent of additive on an active ingredient basis, the balance being lubricating oil or fuel. Such concentrates are convenient for handling the additive when conducting the ultimate blending opera tion to prepare the finished lubricating oil or fuel composition.

I claim:

1. An oil-soluble dispersant additive which comprises the product obtained by reacting an aziridine with a phosphosulfurized hydrocarbon material selected from the group consisting of phosphosulfurized hydrocarbon, phosphosulfurized hydrocarbon which has been hydrolyzed with steam, and phosphosulfurized hydrocarbon which has been reacted with C to C alkanol or a mixture of said alkanol and water; in the ratio of about 1 to 6 moles of said aziridine per atom of phosphorus in said phosphosulfurized hydrocarbon, said phosphosulfurized hydrocarbon being the product of reacting an olefin polymer of about 500 to 100,000 molecular weight with from about 5 to about 40 weight percent of a sulfide of phosphorus; said aziridine being defined by the formula:

RI] R! wherein (a) each of said R, R, R" and R is hydrogen, or (b) R is a C to C alkyl or a C to C aryl group, and R, R" and R" are each hydrogen, or (c) R is a C to C alkyl group and R, R" and R' are each hydrogen.

2. Additive as defined by claim 1, wherein said hydrocarbon is a polymer of a C to C monoolefin.

3. Additive as defined by claim 1, wherein said hydrocarbon is a polymer of isobutylene.

4. Additive as defined by claim 1, wherein said aziridine is ethylenimine.

5. Additive as defined by claim 1, wherein said phosphosulfurized hydrocarbon material is the product of reacting P 5 with polyisobutylene of about 900 to about 3000 average molecular weight, and wherein said aziridine is ethylenimine.

6. Additive as defined by claim 1, wherein said phosphosulfurized hydrocarbon material is said phosphosulfurized hydrocarbon which has been hydrolyzed with steam prior to said reaction with said aziridine.

7. Additive as defined by claim 1, wherein said material is phosphosulfurized hydrocarobn which has been reacted with a C to C alkanol or water prior to reaction with said aziridine.

8. Additive as defined by claim 1, which has been modified by further reaction with a metal salt of a C to C fatty acid or a metal alcoholate of a C to C monohydric aliphatic alcohol in the proportion of about 0.1 to 1 mole equivalent of metal per atom of phosphorus, said metal being selected from the group consisting of zinc, cadmium, and lead.

9. A process for preparing an oil-soluble additive useful as a dispersant in lubricating oil which comprises reacting at a temperature of about 0 to C., for about 1 to 30 hours, an aziridine with a phosphosulfurized hydrocarbon material selected from the group consisting of phosphosulfurized hydrocarbon, phosphosulfurized hydrocarbon which has been hydrolyzed with steam, and phosphosulfurized hydrocarbon which has been reacted with C to C alkanol or a mixture of said alkanol and water, in the ratio of about 1 to 6 moles of said aziridine per atom of phosphorus in said phosphosulfurized hydrocarbon material, said phosphosulfurized hydrocarbon being the product of reacting an olefin polymer of from 500 to 100,000 molecular weight with from about 5 to 40 percent of its weight of a sulfide of phosphorus, said aziridine being defined by the formula:

wherein (a) each of said R, R, R" and R is hydrogen, or (b) R is a C to C alkyl or a C to C aryl group, or (c) R is a C to C alkyl group and R, R and R are each hydrogen.

10. Process as defined by claim 9, wherein said material is phosphosulfurized hydrocarbon reacted with a C to C alkanol prior to reaction with said aziridine.

11. Process as defined by claim 9, which includes the further step of reacting the aziridine-phosphosulfurized 13 14 hydrocarbon material reaction product with a metal c0m- References Cited pound selected from the group consisting of metal al- P coholates of C to C alkanols and metal salts of C to UNITED STATES ATENTS C fatty acids, said metal being selected from the group 3,560,384 2/1971 Hanmg 252-467 consisting of zinc, cadmium, and lead.

12. Process as defined by claim 9, wherein said material 5 LEWIS GOTTS Primary Exammer is phosphosulfurized hydrocarbon hydrolyzed with steam D. R. PHILLIPS, Assistant Examiner prior to reaction with said aziridine.

13. A process according to claim 9, wherein said ma- US. Cl. X.R. terial iS phosphosulfurized polyisobutylene of about 900 10 2 0 139 13 12 252 32 7 E 42 7 4 4 46 7. 44 to 3000 average molecular Weight, and said aziridine is 42 ethylenimine. 

